Abstract:

As a long historic and rich recording country, China has conditions to review the relations among forest, flood, drought and desertification in historic view of thousands of years. Based on the analysis of Chinese historic data, combining with other results of research on history, the floods occurred in Yellow River and Yangtse River basin, drought and desertification enhanced in Northwest China, which resulted from deforestation in large degree, were studied systematically. The result showed: (1) In the past 4 000 a, since human population increase and its unreasonable activities, the percentage of forest cover in China dropped from 60% to 10% or so. The places of deforestation were in Yellow River basin mainly first, then it enlarged to Yangtse River basin and almost all the forest area of China. (2) The mass vanishing of forests in the upper and middle reaches of Yellow River and Yangtse River lead to a series of floods in its middle and lower districts. Its severity degree got much higher as times nearer. (3) The deforestation in Southeast China induced climate drought, precipitation scarcity, lakes dry up and desertification outspread. The equal precipitation line of 400 mm shifted from northwest to southeast. (4) Therefore, in one hand, we should regenerate forest in upper and middle reaches of rivers greatly aims to alleviate floods in middle and lower districts. In another hand, in order to prevent and control the desertification in Northwest China, forest breeding in Southeast China should be implemented and the principal of `step by step' must be followed.

Key words: Deforestation, Flood, Drought, Desertification, Ecological construction, Forest history